During the cold rolling of steel to reduce the thickness thereof for producing strapping and sheeting of various gauges, rolling oil is used to facilitate the cold rolling operation. In industry, a considerable amount of oil is used during the cold rolling operation and must be disposed of periodically. The dimensions of the problem are understood when it is known that in excess of 100,000 gallons of waste rolling oil and water emulsion may be discarded each month in a medium size steel producing facility. This large quantity of rolling oil and water emulsion is costly to dispose of and also presents an environmental hazard if dumped untreated into the sewer system or into lakes or streams.
An additional operation in the production of steel strapping or sheeting is the pickling of the steel with a hydrochloric acid bath. The pickling operation removes mill scale and the like, and it is necessary for the production of good quality unstained sheets and strips. The waste pickle liquor, which contains iron ions therein, also presents a disposal problem, the treatment of which is discussed in U.S. Pat. No. 3,434,797 issued Mar. 25, 1969 to Taylor & Krikau. The disposal problem is aggravated by the fact that perhaps thirty times more waste pickle liquor is produced per month than waste rolling oil and water emulsion.